\newcommand{\myMonth}{Some}
\newcommand{\myDate}[3]{%
\ifthenelse{\equal{#2}{1}}%
{\renewcommand{\myMonth}{January}}{}%
\ifthenelse{\equal{#2}{2}}%
{\renewcommand{\myMonth}{February}}{}%
\ifthenelse{\equal{#2}{3}}%
{\renewcommand{\myMonth}{Marts}}{}%
\ifthenelse{\equal{#2}{4}}%
{\renewcommand{\myMonth}{April}}{}%
\ifthenelse{\equal{#2}{5}}%
{\renewcommand{\myMonth}{May}}{}%
\ifthenelse{\equal{#2}{6}}%
{\renewcommand{\myMonth}{June}}{}%
\ifthenelse{\equal{#2}{7}}%
{\renewcommand{\myMonth}{July}}{}%
\ifthenelse{\equal{#2}{8}}%
{\renewcommand{\myMonth}{August}}{}%
\ifthenelse{\equal{#2}{9}}%
{\renewcommand{\myMonth}{September}}{}%
\ifthenelse{\equal{#2}{10}}%    
{\renewcommand{\myMonth}{October}}{}%
\ifthenelse{\equal{#2}{11}}%
{\renewcommand{\myMonth}{November}}{}%
\ifthenelse{\equal{#2}{12}}%
{\renewcommand{\myMonth}{December}}{}%
\ifthenelse{\isempty{#1}}%
{\myMonth{} #3}%
{\myMonth{} #1, #3}}%